With consumer's increasing demanding for the appearance of electronic display products such as TV, notebook and monitor, a thinner and narrower bezel design of a whole TV is highlighted more and more by consumers.
Currently, a TV of edge-light model quickly occupies an ultra-thin TV market due to an achievement of a thinner TV by reducing the size of light emitting diodes (LED), the thickness of a light guide plate, and the thickness of a prism, as well as using a manner of whole pasting and other ways. However, since the price of a light guide plate in a TV of an edge-light model is relatively high, and the number of LED dies used therein is relatively large, this model has no cost advantage, and cannot have a broader market for a low-end consumer group, although it is easier for that model to reach a thinning purpose.
Contract to an edge-light TV, since the cost of a diffuser plate in a backlight structure of a direct-light TV with a same size is lower, and the number of LED dies is relatively less, a direct-light TV has an apparent advantage in price. However, due to a limitation in design, the closer the distance between the diffuser plate and the LED is, the easier it is to see the LED, resulting in a poor qualification. Moreover, since an emitting angle of the LED is limited, a zone between adjacent LEDs is a non-luminous dark area, which forms an uneven brightness area with a neighbor LED emitting area. Although the diffuser plate and the prism have an effect of diffusion and shielding to the light passing through the diffuser plate and the prism, they are not enough to resolve the problem of uneven brightness. When the pitch between the LEDs is larger, it is easier to appear Mura (shadow) in light paths between adjacent LEDs. Thus, it is required the LED density to be large enough. Therefore, if it is willing to let a TV of direct-light model pass a qualification requirement, a sufficient optical distance (OD) value between the diffuser plate and the reflector should be insured so as to prevent an appearance of a LED Mura. Therefore, although a direct-light TV has an advantage in cost in comparison with the edge-light TV, it has an embarrassing situation that fails to get the market share in the field of ultra-thin TV.